This invention relates to gas turbine engines, and more particularly, to a pulse detonation system for a turbofan engine.
Variable cycle turbofan ramjet engines may be used to provide aircraft flight speeds between low subsonic Mach numbers to high supersonic Mach numbers of about Mach 6. Known engines, as described in U.S. Pat. No. 5,694,768, include a core engine system and a dual mode augmentor. The dual mode augmentor provides additional heat to exhaust airflow exiting the core engine system to increase engine thrust. The core engine system provides power to drive a fan assembly and typically includes in serial, axial flow relationship, a compressor, a combustor, a high pressure turbine, and a low pressure turbine. The dual mode augmentor is positioned downstream from the core engine and receives air from the core engine and a bypass duct surrounding the core engine.
Known engines can operate over a wide range of flight speed operations if several different combustion systems are utilized. During flight speed operations from take-off to approximately Mach 3, the core engine and an engine fan system provide airflow at a pressure and quantity used by the augmentor to produce thrust for the engine. To maintain flight speed operations between Mach 3 and Mach 6, the core engine system is shut-down and ram air flow is introduced into the dual mode augmentor either by windmilling the fan system or by utilizing an auxiliary ram duct. To sustain flight speed operations above Mach 6, either a separate supersonic combustion system, i.e., a scramjet, is used, or a separate rocket-based thrust producing system is used. To achieve flight speed operations in space, the rocket-based thrust producing system is used. As a result, for an engine to operate efficiently over a wide range of operating flight speeds, several different combustion systems are used.
In an exemplary embodiment, a turbofan engine includes a pulse detonation system to provide turbofan engine thrust to permit the engine to operate efficiently over a wide range of operating flight speeds. The pulse detonation system includes a first pulse detonation augmentor which creates a temperature rise and a pressure rise within the turbofan engine to generate turbofan engine thrust. The pulse detonation augmentor includes a shock tube sub-system including a plurality of shock tubes. The shock tubes mix the air and fuel prior to detonating the mixture.
During operation, air and fuel are introduced to the pulse detonation system. The pulse detonation augmentor mixes the air and fuel and detonates the resulting mixture. The detonation produces hot combustion gases which have increased temperature and pressure and are directed from the engine to produce thrust.